1926 Rolex Oyster Advertisement
Rolex invented and patented the first waterproof watch in 1926 and Hans Wilsdorf named it the Rolex Oyster. Today we take waterproof watches for granted, but in 1926 it was a completely revolutionary invention.
The objective with creating a waterproof watch originally was not to make a watch you could swim or take a shower or bath with, but a watch that was completely impervious to all elements. You see, prior to the invention of the Rolex Oyster, watches used to literally rot from the inside out. This would occur because things like humidity, perspiration, grease, dust, dirt, water and oil would get into the watch case and gunk it up.
Also, by allowing air molecules to easily get inside the case, it would dry out the lubrication oil much faster. In the 1920s and 1930s, Rolex would showcase their watches in Authorized Rolex Dealer's windows, but putting the watches on display in fishtanks with real fish to show-off the waterproofness.
The Following Rolex illustration is from 1926: